/**
 * Copyright (C) 2011-2012 The XDocReport Team <xdocreport@googlegroups.com>
 *
 * All rights reserved.
 *
 * Permission is hereby granted, free  of charge, to any person obtaining
 * a  copy  of this  software  and  associated  documentation files  (the
 * "Software"), to  deal in  the Software without  restriction, including
 * without limitation  the rights to  use, copy, modify,  merge, publish,
 * distribute,  sublicense, and/or sell  copies of  the Software,  and to
 * permit persons to whom the Software  is furnished to do so, subject to
 * the following conditions:
 *
 * The  above  copyright  notice  and  this permission  notice  shall  be
 * included in all copies or substantial portions of the Software.
 *
 * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
 * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
 * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
package org.odftoolkit.odfdom.converter.core.utils;

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;

/**
 * This class implements an output stream in which the data is written into a byte array. The buffer automatically grows
 * as data is written to it.
 * <p>
 * The data can be retrieved using <code>toByteArray()</code> and <code>toString()</code>.
 * <p>
 * Closing a <tt>ByteArrayOutputStream</tt> has no effect. The methods in this class can be called after the stream has
 * been closed without generating an <tt>IOException</tt>.
 * <p>
 * This is an alternative implementation of the java.io.ByteArrayOutputStream class. The original implementation only
 * allocates 32 bytes at the beginning. As this class is designed for heavy duty it starts at 1024 bytes. In contrast to
 * the original it doesn't reallocate the whole memory block but allocates additional buffers. This way no buffers need
 * to be garbage collected and the contents don't have to be copied to the new buffer. This class is designed to behave
 * exactly like the original. The only exception is the deprecated toString(int) method that has been ignored.
 * 
 * @author <a href="mailto:jeremias@apache.org">Jeremias Maerki</a>
 * @author Holger Hoffstatte
 * @version $Id: ByteArrayOutputStream.java 610010 2008-01-08 14:50:59Z niallp $
 */
public class ByteArrayOutputStream
    extends OutputStream
{

    /** A singleton empty byte array. */
    private static final byte[] EMPTY_BYTE_ARRAY = new byte[0];

    /** The list of buffers, which grows and never reduces. */
    private List<byte[]> buffers = new ArrayList<byte[]>();

    /** The index of the current buffer. */
    private int currentBufferIndex;

    /** The total count of bytes in all the filled buffers. */
    private int filledBufferSum;

    /** The current buffer. */
    private byte[] currentBuffer;

    /** The total count of bytes written. */
    private int count;

    /**
     * Creates a new byte array output stream. The buffer capacity is initially 1024 bytes, though its size increases if
     * necessary.
     */
    public ByteArrayOutputStream()
    {
        this( 1024 );
    }

    /**
     * Creates a new byte array output stream, with a buffer capacity of the specified size, in bytes.
     * 
     * @param size the initial size
     * @throws IllegalArgumentException if size is negative
     */
    public ByteArrayOutputStream( int size )
    {
        if ( size < 0 )
        {
            throw new IllegalArgumentException( "Negative initial size: " + size );
        }
        needNewBuffer( size );
    }

    /**
     * Return the appropriate <code>byte[]</code> buffer specified by index.
     * 
     * @param index the index of the buffer required
     * @return the buffer
     */
    private byte[] getBuffer( int index )
    {
        return (byte[]) buffers.get( index );
    }

    /**
     * Makes a new buffer available either by allocating a new one or re-cycling an existing one.
     * 
     * @param newcount the size of the buffer if one is created
     */
    private void needNewBuffer( int newcount )
    {
        if ( currentBufferIndex < buffers.size() - 1 )
        {
            // Recycling old buffer
            filledBufferSum += currentBuffer.length;

            currentBufferIndex++;
            currentBuffer = getBuffer( currentBufferIndex );
        }
        else
        {
            // Creating new buffer
            int newBufferSize;
            if ( currentBuffer == null )
            {
                newBufferSize = newcount;
                filledBufferSum = 0;
            }
            else
            {
                newBufferSize = Math.max( currentBuffer.length << 1, newcount - filledBufferSum );
                filledBufferSum += currentBuffer.length;
            }

            currentBufferIndex++;
            currentBuffer = new byte[newBufferSize];
            buffers.add( currentBuffer );
        }
    }

    /**
     * Write the bytes to byte array.
     * 
     * @param b the bytes to write
     * @param off The start offset
     * @param len The number of bytes to write
     */
    public void write( byte[] b, int off, int len )
    {
        if ( ( off < 0 ) || ( off > b.length ) || ( len < 0 ) || ( ( off + len ) > b.length ) || ( ( off + len ) < 0 ) )
        {
            throw new IndexOutOfBoundsException();
        }
        else if ( len == 0 )
        {
            return;
        }
        synchronized ( this )
        {
            int newcount = count + len;
            int remaining = len;
            int inBufferPos = count - filledBufferSum;
            while ( remaining > 0 )
            {
                int part = Math.min( remaining, currentBuffer.length - inBufferPos );
                System.arraycopy( b, off + len - remaining, currentBuffer, inBufferPos, part );
                remaining -= part;
                if ( remaining > 0 )
                {
                    needNewBuffer( newcount );
                    inBufferPos = 0;
                }
            }
            count = newcount;
        }
    }

    /**
     * Write a byte to byte array.
     * 
     * @param b the byte to write
     */
    public synchronized void write( int b )
    {
        int inBufferPos = count - filledBufferSum;
        if ( inBufferPos == currentBuffer.length )
        {
            needNewBuffer( count + 1 );
            inBufferPos = 0;
        }
        currentBuffer[inBufferPos] = (byte) b;
        count++;
    }

    /**
     * Writes the entire contents of the specified input stream to this byte stream. Bytes from the input stream are
     * read directly into the internal buffers of this streams.
     * 
     * @param in the input stream to read from
     * @return total number of bytes read from the input stream (and written to this stream)
     * @throws IOException if an I/O error occurs while reading the input stream
     * @since Commons IO 1.4
     */
    public synchronized int write( InputStream in )
        throws IOException
    {
        int readCount = 0;
        int inBufferPos = count - filledBufferSum;
        int n = in.read( currentBuffer, inBufferPos, currentBuffer.length - inBufferPos );
        while ( n != -1 )
        {
            readCount += n;
            inBufferPos += n;
            count += n;
            if ( inBufferPos == currentBuffer.length )
            {
                needNewBuffer( currentBuffer.length );
                inBufferPos = 0;
            }
            n = in.read( currentBuffer, inBufferPos, currentBuffer.length - inBufferPos );
        }
        return readCount;
    }

    /**
     * Return the current size of the byte array.
     * 
     * @return the current size of the byte array
     */
    public synchronized int size()
    {
        return count;
    }

    /**
     * Closing a <tt>ByteArrayOutputStream</tt> has no effect. The methods in this class can be called after the stream
     * has been closed without generating an <tt>IOException</tt>.
     * 
     * @throws IOException never (this method should not declare this exception but it has to now due to backwards
     *             compatability)
     */
    public void close()
        throws IOException
    {
        // nop
    }

    /**
     * @see java.io.ByteArrayOutputStream#reset()
     */
    public synchronized void reset()
    {
        count = 0;
        filledBufferSum = 0;
        currentBufferIndex = 0;
        currentBuffer = getBuffer( currentBufferIndex );
    }

    /**
     * Writes the entire contents of this byte stream to the specified output stream.
     * 
     * @param out the output stream to write to
     * @throws IOException if an I/O error occurs, such as if the stream is closed
     * @see java.io.ByteArrayOutputStream#writeTo(OutputStream)
     */
    public synchronized void writeTo( OutputStream out )
        throws IOException
    {
        int remaining = count;
        for ( int i = 0; i < buffers.size(); i++ )
        {
            byte[] buf = getBuffer( i );
            int c = Math.min( buf.length, remaining );
            out.write( buf, 0, c );
            remaining -= c;
            if ( remaining == 0 )
            {
                break;
            }
        }
    }

    /**
     * Gets the curent contents of this byte stream as a byte array. The result is independent of this stream.
     * 
     * @return the current contents of this output stream, as a byte array
     * @see java.io.ByteArrayOutputStream#toByteArray()
     */
    public synchronized byte[] toByteArray()
    {
        int remaining = count;
        if ( remaining == 0 )
        {
            return EMPTY_BYTE_ARRAY;
        }
        byte newbuf[] = new byte[remaining];
        int pos = 0;
        for ( int i = 0; i < buffers.size(); i++ )
        {
            byte[] buf = getBuffer( i );
            int c = Math.min( buf.length, remaining );
            System.arraycopy( buf, 0, newbuf, pos, c );
            pos += c;
            remaining -= c;
            if ( remaining == 0 )
            {
                break;
            }
        }
        return newbuf;
    }

    /**
     * Gets the curent contents of this byte stream as a string.
     * 
     * @return the contents of the byte array as a String
     * @see java.io.ByteArrayOutputStream#toString()
     */
    public String toString()
    {
        return new String( toByteArray() );
    }

    /**
     * Gets the curent contents of this byte stream as a string using the specified encoding.
     * 
     * @param enc the name of the character encoding
     * @return the string converted from the byte array
     * @throws UnsupportedEncodingException if the encoding is not supported
     * @see java.io.ByteArrayOutputStream#toString(String)
     */
    public String toString( String enc )
        throws UnsupportedEncodingException
    {
        return new String( toByteArray(), enc );
    }

}
